1. Field
The present disclosure relates to oil and gas exploration and production, and more particularly to a source of neutrons used in measurement while drilling and logging while drilling applications.
2. Description of Related Art
Wells are drilled at various depths to access and produce hydrocarbons such as oil and gas from subterranean geological formations. Particularly, hydrocarbons may be produced from a wellbore that traverses one or more subterranean formations.
In the process of completing such a wellbore, modern drilling operations may include gathering information relating to the conditions encountered downhole. Such information typically includes characteristics of the formations traversed by the borehole, and data relating to the characteristics of the borehole itself. The collection of information can be performed by several methods, including wireline logging, logging while drilling (LWD), measurement while drilling (MWD), drill pipe conveyed logging, and coil tubing conveyed logging.
In wireline logging, a probe or “sonde” is lowered into the borehole after some or all of the well has been drilled. The sonde hangs at the end of a long cable or “wireline” that provides mechanical support to the sonde and also provides an electrical connection between the sonde and electrical equipment located at the surface of the well. In accordance with existing logging techniques, various formation characteristics are measured and correlated with the position of the sonde in the borehole as the sonde is pulled uphole toward the surface.
In LWD or MWD, a drilling assembly includes sensing instruments that measure various parameters of the formation during drilling. While LWD and MWD techniques allow formation measurements to be taken during drilling, drilling operations may create an environment that is hostile to electronic instrumentation or sensor operations.
In drill pipe conveyed logging or coil tubing conveyed logging, logging instruments are mounted on a tubing string that moves the instrument through an existing borehole. The tubing string enables logging of horizontal wellbores without subjecting the logging instruments to the drilling environment.